Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.2.1.108 (lactase)
 2,133 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Lactate production and oxygen consumption were studied in single cell suspension prepared from solid tumours of the black-melanotic (Ma), brown-melanotic (MI) and amelanotic (Ab) melanomas of hamster. Aerobic lactase production was about 5 times higher in the fast growing Ab melanoma than in the slow growing Ma and MI melanomas. Aerobic lactate production in both melanotic hamster melanomas was stimulated by 3-(3,4-dihydroxyphenyl)-L-alanine. This compound was without effect on the cells isolated from amelanotic hamster melanoma. L-Phenylalanine, a known competitive tyrosinase inhibitor reduced the stimulatory effect of L-DOPA on the the lactate production. Oxygen consumption was similar in all three melanomas. The oxygen consumption was inhibited completely by 1 mM potassium cyanide in the Ab melanoma but only in about 1/3 in the Ma and MI melanomas. The Pasteur effect was higher in relative terms and lower in absolute terms in the melanotic melanomas than in the Ab melanoma only . The Crabtree effect was present in the Ab melanoma only. Thus glycolysis measured by aerobic and anaerobic lactic acid formation, and cell respiration, measured by oxygen consumption sensitive to KCN, were both higher in the more malignant, less differentiated Ab melanoma than in the Ma and MI melanomas. The suggestion is presented that the process of melanogenesis influences both aerobic glycolysis and the KCN insensitive consumption in the melanotic hamster melanomas.
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PMID:Biochemical characterization of three hamster melanoma variants--II. Glycolysis and oxygen consumption. 669 97

A "lactase solution" was prepared from Escherichia coli. The mechanism of its action has been studied and changes in the rate of hydrolysis under various conditions investigated. The hydrolysis of lactose by the enzyme approximates the course of reaction of the integrated Michaelis-Menten equation. One molecule of enzyme combines with one molecule of substrate. E. coli lactase is readily inactivated at pH 5.0, and its optimal activity at 36 degrees C. is reached between pH 7.0 and pH 7.5. The optimal temperature for its action was found to be 46 degrees C. when determinations were carried out after an incubation period of 30 minutes. Its inactivation by heat follows the course of a first order reaction, and the critical thermal increment between the temperatures of 45 degrees C. and 53 degrees C. was calculated to be 56,400 calories per mol. The enzyme is activated by potassium cyanide, sodium sulfide, and cysteine, and irreversibly inactivated by mercuric chloride, silver nitrate, and iodine. After inactivation with copper sulfate partial reactivation is possible, while the slight inhibition brought about by hydrogen peroxide is completely reversible. The possible structure of the active groups of E. coli lactase as compared with other enzymes has been discussed.
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PMID:STUDIES ON THE LACTASE OF ESCHERICHIA COLI. 1987 23